A. The Pearl itself
a. Pearl: A pearl is a lustrous organic gem. It is formed within one of the parts of soft tissue called mantle of certain mollusks (primarily oysters and mussels). The formation is initiated as a defense mechanism whenever an irritant such as sand or parasite enters the soft tissue of a mollusk. The mantle of the mollusk isolates the irritant by depositing layers of nacre, secreted by the mollusk’s mantle.
They come in many shapes, sizes and colours.
b. Natural Pearl
Pearls that form naturally in mollusks in wild, in oceans, without human intervention. These are extremely rare now.
c. Cultured pearl: A pearl formed by human intervention, by artificially introducing an irritant into the soft tissue of a mollusk.
1. Saltwater Pearl: A pearl which is produced by oysters in ocean.
2. Freshwater Pearl: A pearl which is produced in freshwater like rivers, lakes etc.
d. South Sea Pearl
A type of cultured pearl grown in saltwater oysters (Pinctada maxima) of Australia, Indonesia, Philippines. They are known for their large size and vibrant colours.
These pearls are usually the most expensive of the three saltwater cultured pearls. They have the thickest nacre.
e. Akoya Pearl
A type of cultured pearl grown in saltwater oysters (Pinctada fucata). They are known for their perfectly spherical shape, good lustre but smaller size. They typically vary from 2mm to 10mm in size. Primarily grown in Japan and now also in China and Vietnam. Available in mostly white with rose overtone.
f. Tahitian Pearls
These are saltwater cultured pearls formed in the Pinctada Margaritifera oysters (black-lipped), primarily found in French Polynesia-a group of islands in South Pacific. Known for their dark shades including black and gray and rich overtones. They have relatively bigger size than Akoya but smaller than South Sea pearls. They vary from 8mm up to 20mm (rare) and commercially in huge demand.
g. Keshi Pearls
They are small pearls which form as a byproduct of the culturing process. They can develop both in the saltwater and freshwater mollusks. These pearls consist entirely of nacre and therefore exhibit high lustre.
h. Blister Pearls
Unlike normal pearls, which form in the soft tissue of the mollusk (mantle), they form when the irritant gets lodged between the mantle and the inner surface of the shell (mother of pearl). Nacre is secreted over the irritant.
The pearl in this case becomes attached to the shell surface forming a blister-like appearance.
Typically, they have a dome-like or hemispherical appearance with a flat back. Jewellery makers often cut away the shell, remove or grind down the nucleus and fill the cavity. They are used in jewellery where the shell is part of the design.
i. Mabe Pearls:
These are cultured blister pearls. A half-bead nucleus is inserted on the inside of the shell (between the mantle and the shell inner surface). Nacre is secreted over the nucleus, forming a cultured blister pearl. This blister pearl is then cut away from the shell, processed and used in various types of jewellery, including earrings, pendants, rings and brooches.
j. Seed Pearls
Seed pearls are small pearls, measuring 2mm or less in diameter.
Seed pearls both in natural and cultured form exist. The size of the irritant impacts the size of the pearl. Natural seed pearls are formed when the size of the irritant is usually microscopic. Natural seed pearls are rare because it entirely depends on chance encounters between the mollusk and tiny irritants.
Cultured seed pearls are generally by product of the main pearl formation, when the implanted bead is dislodged because of some reason. It triggers irritation in other parts of the mollusk, leading to nacre secretion in unexpected places. Sometimes, accidentally, a tiny piece of the mantle tissue of the donor mollusk gets inserted along with the bead. This when tears off and is free, tumbles here and there around the mollusk leading to formation of many tiny pearls. Each time the tissue fragment settles at a new place, it leads to formation of a tiny little pearl. The imperfect isolation is what allows for the creation of these seed pearls. It is interesting that how an organisms’ natural defenses can sometimes lead to unexpected and beautiful outcomes.
k. Baroque Pearls
This is a broad category for irregularly shaped pearls. These pearls have no symmetrical shapes. There are many reasons for such unrestrained pearl shape formation. Natural baroque pearls are formed because of irregular development of pearl sac. In cultured pearls, it may be because of the shape of the bead which is inserted in the mollusk or other natural reasons beyond the control of the pearl farmers.
l. Abalone
Abalone pearls are of saltwater origin. Abalone are not oysters. They belong to different classes within the mollusk species.
It is a name given to those pearls that are found in the univalve shell, a type of marine snail with a single ear-shaped shell called awabi in Japan. They are rarely round, generally flat or irregular in shape. They are generally green, blue green or fawn-yellow and have an intense red, flame like iridescence. Culturing abalone pearls is difficult. Abalone pearls are extremely rare in the wild also. Because of rarity, abalone pearls are expensive.
Abalone creatures thrive in cold, rocky coastal waters of North America, South Africa, Australia, Japan.
m. Conch
These are unique non-nacreous type of pearls, which are found in the univalve shell (strombus gigas), which is pink conch or the common conch and yellow shell (cassis madagascarensis), the yellow shell.
Conch pearls are non-nacreous. They have unique inner structure that gives them a different lustre, often described as flame like.
B. Pearl Formation & Cultivation
1. Irritant
An irritant in pearl formation is any foreign body (sand grain, parasite), which when comes in contact with the soft tissue of a mussel irritates the defence system of the mollusk triggering secretion of nacre to isolate the irritant.
2. Nacre
It is a vital substance which makes a pearl.
Nacre is the term used for the iridescent material that is secreted by mollusks, including saltwater oysters and freshwater mussels.
Nacre is primarily made up of aragonite (a mineral form of calcium carbonate) and Conchiolin (a protein)
3. Mother of Pearl
The pearl-bearing mollusks are luxurious creatures because of the fact that they produce pearls, which are full of beauty and elegance. No matter how ugly and foul these mollusks look from outside but for the purpose of protecting their delicate bodies, they cover the interior of their shells with a smooth lustrous material, mixed with rainbow hues. This material is called mother of pearl or nacre, which Is the same substance which is found in pearls.
Nacre consists of accumulation of extremely thin semi-transparent films of laminae of granular organic substance called conchiolin with the interstices filled with calcareous matter (aragonite)
The Nacre decrease in thickness from the hinge toward the lip of the shell and terminates as short distance from the extreme edge.
4. Conchiolin
It is an organic protein, primarily composed of amino acids, which binds together the mineral constituents of the shell or the pearl. It acts as the bonding agent between different layers of aragonite, contributing to the strength of the pearl
5. Aragonite
Aragonite is a crystalline form of calcium carbonate (CaCO3).
Nacre basically consists of two main constituents, Aragonite and Conchiolin. Aragonite provides structural strength and iridescence to the pearl whereas Conchiolin acts as a bonding agent between different layers of Aragonite.
6. Graft Tissue
It is used in the formation of cultured pearls. It is a small piece of mantle tissue from the donor mollusk, which is grafted into the mantle tissue of the mollusk used for pearl formation. The graft tissue triggers the pearl formation process in the recipient mollusk.
7. Nucleus
It is a small object, typically a bead, often made of mantle tissue (sometimes synthetic beads are also introduced) inserted in the mollusk for formation of round pearls. The inserted bead nucleus acts as an irritant and triggers the defence mechanism of the recipient mollusk.
In cultured freshwater pearl farming, farmers generally introduce only graft tissue of the mantle because freshwater mussels produce more nacre than oysters. While in case of saltwater pearls, there is a practice of introducing both the bead nucleus and the graft. Nucleus is for formation of rounded pearls whereas mantle graft aids in production of more nacre for quality pearl formation.
8. Pigtoe Clam
Some mussels are used for nucleus production for making cultured pearls. These mussels within the Pleurobema genus are called Pigtoes. They have thick shells and are suitable for nucleus production.
9. Pearl Sac
A sac-like structure formed around the irritant in a mollusk. It is primarily formed from the mantle tissue (but separate from it), which is responsible for nacre secretion. Pearl Sac envelops the irritants, isolates it and covers it by layers of nacre over a period of time.
Pearl Sac formation sets in to isolate the foreign body or the irritant, which enters the mantle tissue of the mollusk.
10. Pearl Farm
Pearl farm is an aquaculture facility, where pearls are artificially grown using mussels (freshwater pearls) and oysters (saltwater pearls).
Pearl farming can take place both in both freshwater and saltwater systems. Pearl farming requires a scientific management of water quality, the health of mollusks, water temperature etc. to ensure successful pearl growth. Since pearl formation is a completely biological process, a careful management is needed to maintain a robust ecosystem.
C. Pearl Characteristics
I. Orient of the Pearl
It is an important quality of the pearl. It describes the unique and captivating play of colours when light falls on the pearl’s surface. The light passes through different layers of the nacre in the pearl and display different colours because of interference and diffraction of light when it falls on the pearl surface.
Orient of the pearl depends on the nacre thickness, nacre quality, shape of the pearl and surface quality of the pearl.
II. Lustre
It is the brilliance of the surface of the pearl, the quality of the pearl to reflect light brightly and sharply. Lustre also depends on nacre thickness, smoothness of its surface and nacre quality.
Both lustre and orient are important factors in evaluating quality of the pearl.
III. Surface Quality
Fundamentally, surface quality of a pearl refers to the imperfections on the pearl’s surface. Common imperfections are spots, scratches, bumps, pits, chips and wrinkles. A smooth surface allows better reflection of light, and it eventually impacts the pearl quality.
IV. Pearl Grade
Pearl grading is a process to evaluate pearl quality. It is a standardized way to assess the pearls and attach a value to them. Key factors in pearl grading are lustre, surface quality, shape, colour, size, nacre thickness and pearl matching.
V. Pearl Grading System
A set of grading systems in vogue for categorizing and comparing pearl quality. There are 3 systems most widely accepted worldwide, though there are other systems also in use in Japan and China
1. The A-AAA system, which primarily uses lustre, surface quality and shape.
· Commonly used for freshwater and Akoya pearls
· AAA- Excellent lustre, smooth surface (95% blemish free)
· AA- High lustre, blemish free (75%)
· A- Medium to low lustre with noticeable blemishes
2. The A-D system
Developed for Tahitian pearls but also applied to South Sea pearls also. Stronger emphasis on surface quality. A grade means very high lustre, very few blemishes. B grade means high to medium lustre with minor blemishes (less than 30% of the surface). C is medium lustre with less than 60% blemishes of the surface and D is lowest grade.
3. GIA Pearl grading system
Developed by Gemological Institute America. It is more comprehensive and evaluates a pearl on the basis of all the criteria, shape, size, lustre, surface quality, nacre, surface quality, matching
VI. Shape
Pearl shape refers to the geometrical outline of the pearl and is one of the important criteria for evaluating a pearl quality. Some pearl shapes are spherical, baroque and blister pearls.
VII. Size
Pearl Size is about a pearl’s dimensions, and it gives information about how big or small is. It is expressed in millimeters (mm). It is a quantifiable characteristic of a pearl, which impacts its value.
For understanding more on pearl size see Totapari’s blog on pearl size.
VIII. Colour
This is the dominant overall colour of the pearl, the first colour impression when you see a pearl. The main pearl colours are Cream, Silver, Grey, Black Gold, Blue, Rose etc. It depends on factors like mollusk species, the organism in which it is formed, environment (water temperature, food source, minerals), human interventions (dying, bleaching etc.)
D. Pearl Treatments & Enhancements
1. Pearl Bleaching
It means making the colour of pearl light using a chemical solution, usually hydrogen peroxide
2. Pearl Dyeing into the nacre
Dyeing a pearl means changing the colour of the pearl by introducing a colouring agent. It is done by soaking the pearls in a dye solution, under controlled temperature and pressure, allowing the dye to penetrate the nacre layers.
There are specialized equipment to do it, for precise control of both temperature and pressure.
3. Pearl Coating
Pearl coating is a surface treatment. It involves applying thin layer of a material (lacquer, resin, polymers) done to enhance lustre, mask blemishes and alter the colour. This is ususlly done in imitation pearls to make them look more real.
4. Irradiation
Irradiation in case of pearl means exposing pearls to a source of radiation, typically gamma rays from cobalt-60 source, to alter the colour of the pearl. It is done to darken the basic shade of the pearl, often black, dark gray or deep golden yellow. It is generally a permanent treatment for altering the colour.
It is difficult to detect irradiation without using advanced gemological equipment, not available to the ordinary customers.
E. Pearl Jewellery
1. Pearl Necklace
A piece of jewellery worn around the neck, which consists of a string of pearls often with a clasp. It can vary in length and style, from single strand to multiple strands to elaborate designs.
2. Pearl Earrings
Jewellery pieces worn on the ears, featuring one or more pearls as the main element. They can be studs, hoops or drops, attached to the earlobe by a post, wire or clip.
3. Pearl Ring
A circular band made of metal, worn of a finger, featuring one or more pearls. If the pearl is of big size, then it generally has one pearl as the main attraction. The metal can be silver, gold, titanium etc.
4. Pearl Bracelet
A piece of jewellery worn around the wrist, typically consisting of a series of pearls, linked together with a wire or set in a metal frame.
F. The Organism and its Anatomy
1. Mollusk: Mollusks are a diverse group of soft-bodied animals, many of which have shells. The group mollusk includes familiar creatures like snails, squids, oysters and mussels. While some are known for being delicious seafood (like clams and mussels), others, particularly oysters, are famous for their ability to create pearls. Beyond pearls and food, some shells are used for decorative purposes. They also play an important role in cleaning water and protect environment.
2. Oyster: Oysters are bivalves (two-shelled mollusks), known for two main things: their ability to product pearls and their talent for filtering water. As they feed they filter out algae and other particles, helping to keep coastal waters clean and clear.
3. When an irritant (like a grain of sand) enters the oyster's shell, it coats it with layers of nacre, forming a pearl. Oysters are also a popular seafood delicacy enjoyed worldwide.
4. Mussel: They are bivalve mollusk, similar to oysters in their filter-feeding habits. They attach themselves to surfaces using strong threads. While some mussels can produce pearls, they are not as commercially valuable as oyster pearls. Mussels are primarily known as a popular and affordable seafood.
5. Black-lipped Oyster: The Artist Behind the Dark Gems (Tahitian Pearls): The black-lipped oyster (Pinctada margaritifera) is the source of stunning black pearls, often called Tahitian pearls. These oysters live in warm tropical waters and are specifically farmed for their unique dark-colored gems, which are highly valued in jewellery.
6. Golden-lipped Oyster: The Source of South Sea Sparkle (Large and Luxurious Pearls): The golden-lipped oyster (Pinctada maxima) is the largest pearl oyster and produces the luxurious South Sea pearls. These pearls are known for their large size, beautiful lustre, and colours ranging from white to gold. These oysters are specifically cultivated in pearl farms for this purpose.
7. Soft Tissue: The Oyster's Inner Workings (Essential for Pearl Formation): The soft tissue is everything inside the oyster (organs, muscles and the mantle) but not the shell. The health of this tissue is crucial for pearl formation. The mantle, a part of the soft tissue, is directly responsible for creating the nacre that forms the pearl.
8. Mantle: It is part of the soft tissue of the mollusk. The Pearl-Making Machine (Layer by Layer): The mantle is a thin layer of tissue that lines the inside of the shell of a mollusk and is responsible for secreting nacre. More importantly, it's the part that creates the pearl by coating an irritant with layers of nacre (mother of pearl).
9. Mother of Pearl (Nacre): The Shimmering Secret Ingredient (Making Pearls and Shells Beautiful): Mother of pearl, or nacre, is the iridescent inner layer of some shells. It's made of layers of minerals and proteins and gives pearls their unique shine and lustre. It's also used in decorative inlays and other artistic applications.
10. Bivalve: The Two-Shell Club (Some Make Pearls, Many Are Food): Bivalves are mollusks with two hinged shells. This group includes oysters, mussels, clams, and scallops. Some bivalves, like oysters and some mussels, are capable of producing pearls, while many others are important food sources.
11. Univalve: The One-Shell Wonders (Mostly Snails - Not Pearl Producers): This term refers to mollusks with a single shell, usually coiled, like snails. Univalves are not known for producing pearls. Some are considered pests in gardens, while others are eaten in certain cultures.
12. Gastropods: The Belly-Footed Crew (Not Pearl Producers, Diverse Uses): Gastropods, including snails and slugs, are a large group of mollusks. They are not involved in pearl production. Some are used as food (like escargots), while others play important roles in ecosystems as decomposers.
13. Cephalopods: The Smart and Speedy Ocean Dwellers (No Pearls, but Important in the Food Chain):Cephalopods like squids and octopuses are not related to pearl production. They are important predators and prey in marine ecosystems and are also a food source in many parts of the world.
14. Pinctada maxima: The Queen of Pearl Oysters (South Sea Pearls): This is the largest pearl oyster and the producer of highly valuable South Sea pearls. These oysters are specifically farmed for their pearl production and are a significant part of the pearl industry.
15. Pinctada margaritifera: The Black Pearl Specialist (Tahitian Pearls): This oyster species is farmed specifically for the production of black pearls, known as Tahitian pearls. These unique gems are highly sought after in the jewellery market.
16. Pinctada fucata: The Maker of Classic Akoya Pearls (Cultivated for Jewellery): These oysters are cultivated for producing Akoya pearls, which are known for their classic round shape and high lustre. They are widely used in jewellery making.
Pearl Cultivation
Pearl cultivation, also known as pearl farming or pearl culture, is the human process of inducing pearl formation in mollusks, typically oysters or mussels, for commercial purposes. It's essentially a way of "farming" pearls instead of relying solely on the rare occurrence of natural pearl formation.
G. Scientific, Historical & Cultural Significance
- Mikimoto Kokichi
Mikimoto Kōkichi (1858-1954) was a Japanese entrepreneur who is widely credited with developing the technique for cultivating pearls and establishing the cultured pearl industry. He is often referred to as the "Pearl King."
- La Peregrina Pearl
La Peregrina is one of the most famous pearls in the world, with a rich history spanning centuries and connections to royalty and Hollywood. Its name, meaning "The Wanderer" or "The Pilgrim" in Spanish, reflects its journey through different owners and countries.
Here are some key facts about La Peregrina:
Discovery: It was reportedly discovered in the mid-16th century in the Gulf of Panama by an African slave, who was rewarded with his freedom for the find.
Appearance: La Peregrina is a large, pear-shaped pearl with a remarkable size and symmetry. It originally weighed 223.8 grains (55.95 carats, or 11.2 grams). After cleaning and drilling in 1913, its weight was slightly reduced to 203.84 grains.
Royal Connections:
· It was given to King Philip II of Spain and became part of the Spanish Crown Jewels.
· It was owned by several Spanish queens, including Mary I of England (also known as Mary Tudor or "Bloody Mary"), who received it as a gift from Philip II.
· During the Napoleonic Wars, the pearl passed into the hands of Joseph Bonaparte, Napoleon's brother.
· It later belonged to the Dukes of Abercorn, a British aristocratic family.
· Elizabeth Taylor: In 1969, actor Richard Burton purchased La Peregrina for $37,000 as a Valentine's Day gift for his wife, Elizabeth Taylor. Taylor, a renowned jewellery lover, had the pearl set into a beautiful necklace designed by Cartier.
· Auction and Current Ownership: After Elizabeth Taylor's death in 2011, La Peregrina was auctioned at Christie's in New York for a staggering $11.8 million, setting a record price for a pearl at auction. It is now in a private collection.
La Peregrina is not only a beautiful and valuable gem but also a historical artifact that has witnessed significant events and been owned by prominent figures throughout history. Its journey from a Panamanian pearl bed to the hands of royalty and Hollywood royalty has cemented its place as one of the world's most iconic pearls.
